Every year on the third Monday in January, the United States celebrates the memory of slain civil rights leader Martin Luther King, Jr.

King first rose to prominence in 1955 when he led a successful boycott of the public buses in the southern city of Montgomery, Alabama, forcing the city to end its practice of segregating black passengers.

He became the central figure of the Civil Rights Movement of the 1950s and '60s, inspiring millions with his famous "I Have a Dream" speech during the 1963 March on Washington.

Service projects

Many around the country spend the holiday commemorating King's tireless work to end racism and promote civil rights by participating in community service projects.

This year that included President Barack Obama and First Lady Michelle Obama, who visited a Washington, D.C., elementary school where they got their hands dirty helping plant vegetables like spinach in raised garden beds.

The Obamas were joined by White House mentees and members of AmeriCorps in packing bags with school supplies for the students, many of them from military families.

In 1994, Congress designated the King holiday as a national day of service. So on Monday, many Americans who had the day off from work helped their communities to commemorate King's legacy.

"We have about 500 volunteers mobilized today for the MLK day of service," said Molly Hahn, a volunteer coordinator for the organization "Hands On" in central Texas.

Those volunteers helped pick up trash from the streets of Austin, Texas.

"We have about 333 people that are doing a litter cleanup along MLK Boulevard. It is many miles and they are splitting up into groups of 50 to make sure all the trash gets cleaned up," Hahn said.

The organizers said there is no better way to honor King's life.

"Four-hundred-fifty people from all over the city, all communities in the city, all walks of life, all ethnicities, all races, all genders, all everything, combined together, to make the community a little bit better," said Steve Adler, mayor of Austin, Texas.

Marches in New York, Florida

Meanwhile, in New York City, dozens of students and parents marched on a chilly morning along Central Park to honor the civil rights leader.

"The mission of this school was based on the principles of Martin Luther King for racial and economic equality,” said Lisa Edwards, one of the parents who joined the march. “So that means diverse student body, diverse staff, and a body that also includes members of all different classes. And those are the principles I wanted my daughter to grow up with."

In milder temperatures, hundreds gathered for a parade in Miami, Florida. Marching bands, dancing groups and dozens of people with different world flags were part of the celebration.

At the end of the parade, 600 backpacks with free school supplies were handed out to students in need.

"We want to see unity in the community and make sure the next generation is aware of all of his sacrifices," said Barbara Barber, one of the organizers.

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Martin Luther King, Jr.

King's birthday celebration this year comes as a predominately African-American town in Michigan learns that it was not told for 1½ years that its residents had been drinking lead-contaminated water, putting the population — especially young children — on the path to irreversible illnesses.

Civil rights leader Jesse Jackson described Flint, Michigan, as a "crime scene." Documentary filmmaker Michael Moore said the situation in his hometown is a "racial crisis" and a "poverty crisis."

Volunteers across Michigan commemorated the Monday holiday with acts of service, including delivering bottled water to residents of Flint.

The National Association for the Advancement of Colored People, or NAACP, said in a statement Sunday, "To expose an entire city of nearly 100,000 residents, many of them children, to toxic lead is, if not criminal, is at the very least inhumane. ... Would more have been done, and at a much faster pace, if nearly 40 percent of Flint residents were not living below the poverty line? The answer is unequivocally yes."

King won the Nobel Peace Prize in 1964 for leading the civil rights movement in the United States.

Many here in Washington say this is not a day off — but a day on to help one another.